Interlocking construction for arc chute housing



Aug. 3, 1965 E. WORTMANN 3,198,915

INTERLOCKING CONSTRUCTION FOR ARC GHUTE HOUSING Filed July 17. 1961 3 Sheets-Sheet l IN VEN TOR. L I/V557 Wd/BrnMA/n' Aug. 3, 1965 E. WORTMANN INTERLOCKING CONSTRUCTION FOR ARC CHUTE HOUSING Filed July 17. 1961 3 Sheets-Sheet 2 Aug. 3, 1965 E. WORTMANN INTERLOCKING CONSTRUCTION FOR ARC CHUTE HOUSING Filed July 17. 1961 3 Sheets-Sheet I5 INVEN TOR. E F/YEJT waer/mwv v BY 0 7x44 la 1 5752!, fans f JIFAEW United States Patent 1 3,198,915 INTERLOQKING CONSTRUETION FOR ARC CHUTE HOUSING Ernest Wortmann, Drexel Hill, Pa., assignor to i-T-E (Iircuit Breaker Company, Philadelphia, Pa., 21 corporation of Pennsylvania Filed July 17, 1961, Ser. No. 124,411 10 Claims. (Cl. 200-144) This invention relates to molded case circuit breakers in general and more particularly to a novel construction for the are chute and flash barrier thereof.

When an arc is drawn between the parting cooperating contacts of a circuit breaker this are passes into an arc chute constructed to rapidly extinguish the arc. The typical arc chute comprises a stack of spaced plates having tapered notches at the front ends thereof.

Molded case circuit breakers are usually constructed of phenolic which is a good dielectric material. However, when phenolic is charred its dielectric properties are seriously impaired. If the are drawn between the parting cooperating contacts contacts the housing directly, or indirectly by heating particles which contact the housing, then the housing material becomes charred and no longer functions as a good dielectric. Accordingly, it is necessary to place a flash barrier at the front of the arc chute to confine the arc and arcing products within the arc chute.

A flash barrier is typically of a U-shaped member positioned so that the plane of movement of the movable contact arm is perpendicular to the plane of the flash barrier and positioned between the arms of the U. The flash barrier is usually constructed of black fiber which is a material whose dielectric characteristics are maintained even after it is subjected to extremely high temperatures. However, this material has a tendency to absorb moisture. When this occurs the arms of the U tend to converge often interfering with movement of the movable contact arm.

In order to overcome this undesirable effect the instant invention provides an arc chute housing whose sidewalls include extensions which are positioned between the U arms of the flash barrier near the upper ends thereof. By so positioning the sidewall extensions, even if the flash barrier should absorb moisture the U arms are prevented from collapsing since the sidewall extensions are in blocking position. The sidewalls of the arc chute are constructed of melamine which are not adversely affected by moisture.

In this invention the arc chute housing is comprised of three separate members, two sidewalls and a back- Wall. The sidewalls are fixedly secured to the arc plates with assembly being facilitated in that spacing means for the arc plates at the front and back thereof may be maintained in position until securement of the sidewalls to the arc plates is complete.

The sidewalls at the upper backs thereof are provided with pockets having bottom openings to receive the upper end of the backwall for maintaining the latter in operative position.

The back edges of the sidewalls are so related to the pockets that the backwall when in its relaxed or flat position is for the most part spaced from the sidewall back edges. However, the terminal strap carrying the stationary contact is stepped, with the step providing means for bending the backwall so that it abuts a substantial interfering portion of the sidewall back edges and in so doing the backwall is tensioned to be maintained in operative position without undue freedom of movement.

Accordingly, a primary object of this invention is to provide a molded case circuit breaker having a novel are chute construction which is economical to produce and is etficient in operation.

Another object is to provide a molded case circuit breaker having novel means for maintaining the arms of the flash barrier in operative position.

Still another object is to provide an arc chute construction wherein the housing is constructed of three sheet-like members, one of which is interlocked with the other two.

A further object is to provide an arc chute whose sidewalls are provided with forwardly extending portions positioned between the arms of a flash barrier to prevent converging thereof should the flash barrier be subjected to moisture.

A still further object is to provide a novel construction in combination for a flash barrier constructed of an insulating material which ra-pidly deforms when subjected to moisture and an arc chute housing constructed of another insulating material which will not deform when subjected to moisture.

These as well as other objects of this invention shall become readi y apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a perspective of a molded case circuit breaker constructed in accordance with the teachings of the instant invention with the cover thereof being removed to reveal the internal construction.

FIGURE 2 is a longitudinal cross section taken through line 22 of FIGURE 1 looking in the direction of arrows 2-2.

FIGURE 3 is a side elevation of an arc chute of the circuit breaker of FIGURE 1.

FIGURE 4 is a rear view of the arc chute of FIGURE 3 looking in the direction of arrows 44.

FIGURE 5 is a plan view of the arc chute of FIG- URE 3.

FIGURE 6 is an elevation of the flash barrier illustrating the position of the arc chute housing.

Now referring to the figures, circuit breaker 10 comprises a molded housing having a base 11 and removable cover 12. Base 11 is provided with longitudinal partitions 14, 15 which divide base 11 into three elongated compartments, one for each phase of circuit breaker 10. Similar longitudinal partitions (not shown) are provided for cover 12.

The current path through each phase of circuit breaker 10 comprises load terminal connector 16, load terminal strap 17 including loop portion 18 having portion 20 of reduced cross sections which serves as a heater for bimetal trip element 21 connecting member 22, flexible member 23 to one end of movable contact arm 24. Movable contact 25 is mounted to the other end of contact arm 24 and is engageable with stationary contact 26 mounted to one end of line terminal strap 27 which is connected by screw means 29 to tulip connector 28 form ing the line terminal connection.

Trip free operating mechanism 30 is provided to pivot movable tie bar 99 about pin 36. All three contact arms 24 are carried by tie bar Q9 for simultaneously operating movable contacts 25 of all three phases into and out of engagement with their associated stationary contacts 26. Gperating mechanism 30 is of an overcenter toggle type well known to the art and is fully described in copending application, Serial No. 108,812, filed May 9, 1961, entitled U-Shaped Cradle for Circuit Breaker, invented by Ernest R. Wortmann, and assigned to the assignee of the instant invention. Handle 98 is provided for manual operation of mechanism 30 while overload device 97 is provided for automatic tripping of mechanism 30.

Arc extinguishing means in the form of arc chute is operatively positioned by suitable formations in base 11 resistant dielectric material such as black fiber.

3 to receive electric current arcs drawn between cooperating contacts 25, 26 upon separation thereof. Since the theory of arc interruption is well understood to those skilled in the art elaboration of this point will not be undertaken at this time.

Arc chute it comprises a stack of spaced metal plates 41 constructed of magnetic material and provided with tapered notches 4-2 communicating with the front edges thereof. Each of the plates 41 is provided with outwardly extending tabs 43, 44 which, after passing through appropriately positioned apertures in sidewalls 45, 46 of the arc chute housing, are deformed to rigidly secure arc plates 41 to sidewalls 45, 46.

sidewalls 45, 46 include rearward extensions 47, 48, respectively, defining pockets 53, 54 which are open at the bottoms thereof. The arc chute housing further includes backwall 49 comprising a plate-like member which in its relaxed condition (phantomed in FIGURE 3) is fiat. The back edges of sidewalls 45, 46 are sloped at St) to provide interfering portions. Sloping portions are so positioned that backwall 49 when fiat and having the upper edges thereof within pockets 53, 54 can only engage sloping portions 59 at the tops thereof.

With arc chute 4G operatively positioned within base 11 the abruptly rising stepped portion 55 of line terminal strap 27 bends backwall 4-9 so that it rises against sloping portion 50, as best seen in the solid line position of FIG- URE 3. This deformation of backwall 49 supplies a tensioning action whereby backwall 49 fits snugly against sidewalls 45, 46 to minimize the movement of backwall 49. It is noted that the backwall portions which are disposed within pockets 53, 54 are notched at 5'7, 58, respectively, to prevent sidewise movement of backwall 49.

In order to confine the arc and arcing products to arc chute 40 the front thereof is partially closed by flash barrier 69 which is a generally U-shaped member whose side edge extensions 61, 62. are disposed within vertical slots 63, 64, respectively of base Ill. The upper ends of the U arms are provided with notches d5, 66, respectively which receive the forward extensions 67, 68, respectively of sidewalls 45, '46, respectively.

It is noted that flash barrier 60 is constructed of a heat While this material has extremely good electrical properties, should this material be subjected to moisture, warpage takes place. In the case of a U-shaped member, this warpage causes the upper ends of the U arms to converge. Since the plane of movement 64 of movable contact arm 24 is midway between the U arms, if the U arms converge sufficiently they will interfere with movement of contact arm 24.

The are chute housing sidewalls 45, 46 as well as backwall 49 thereof are each constructed of an insulating material such as melamine which will retain its shape even after being subjected to moisture.

As best seen in FIGURE 6, forward extensions 67, 68 of sidewalls 45, 46, respectively are positioned between the arms of flash barrier 60 so that as the U arms begin to converge the convergence is blocked by extensions 67, 68 and because of this movable contact arm 24 is not interfered with.

As is also clearly seen in FIGURE 6, the positioning of extensions 67, 68 within notches 65, 66 operatively positions flash barrier 60. That is, in this manner flash barrier 60 is prevented from moving upward out of slots 63, 64.

Thus, this invention provides a novel interlocking construction for an arc chute housing and also provides a novel combination of arc chute housing and flash barrier whereby the flash barrier may be constructed of a single U-shaped member of heat resistant insulating material, even one which readily absorbs moisture. The are chute housing is constructed to block warpage of the fiash barrier thereby preventing the flash barrier from interfering with movement of the movable contact arm.

In the foregoing, the invention has been described only in connection with preferred embodiments thereof. Many variations and modifications of the principles of the invention within the scope of the description herein are obvious. Accordignly, it is to be found not by the specific disclosure herein but only by the appending claims.

I claim:

1. A circuit breaker comprising a pair of cooperating contacts and an arc chute operatively positioned and constructed to receive and extinguish electric current arcs drawn between said cooperating contacts upon separation thereof; said are chute comprising a plurality of spaced plates and a housing wherein said plates are disposed; said housing comprising spaced sidewalls to which said plates are fixedly secured along the side edges thereof; said sidewalls having rearwardly extending portions defining pockets open at the bottoms thereof; said housing also comprising a backwall whose upper end is entered into said pockets to prevent upward movement of said backwall.

2. A circuit breaker comprising a pair of cooperating contacts and an arc chute operatively positioned and constructed to receive and extinguish electric current arcs drawn between said cooperating contacts upon separation thereof; said arc chute comprising a plurality of spaced plates and a housing wherein said plates are dis posed; said housing comprising spaced sidewalls to which said plates are fixedly secured along the side edges thereof; said sidewalls having rearwardly extending portions defining pockets open at the bottoms thereof; said sidewalls having interfering sloped portions at the back edges thereof below said pockets; said housing also comprising a backwall whose upper end is entered into said pockets to prevent upward movement of said backwall; said backwall being flat when removed from said pockets; first means bending said backwall to abut said sloped portions.

3. A circuit breaker comprising a pair of cooperating contacts and an arc chute operatively positioned and c011- structed to receive and extinguish electric current arcs drawn between said cooperating contacts upon separation thereof; said are chute comprising a plurality of spaced plates and a housing wherein said plates are disposed; said housing comprising spaced sidewalls to which said plates are fixedly secured along the side edges thereof; said sidewalls having rearwardly extending portions defining pockets open at the bottoms thereof; said sidewalls having interfering sloped portions at the back edges thereof below said pockets; said housing also comprising a backwall Whose upper end is entered into said pockets to prevent upward movement of said backwall; said backwall being flat when removed from said pockets; first means bending said backwall to abut said sloped portions; said backwall having an upper portion disposed between said sidewall rearwardly extending portions; said backwall for the major portion of its length abutting the sidewall back edges.

4. A circuit breaker comprising a pair of cooperating contacts and an arc chute operatively positioned and constructed to receive and extinguish electric current arcs drawn between said cooperating contact upon separation thereof; said are chute comprising a plurality of spaced plates and a housing wherein said plates are disposed; said housing comprising spaced sidewalls to which said plates are fixedly secured along the side edges thereof; said sidewalls having rearwardly extending portions defining pockets open at the bottoms thereof; said sidewalls having interfering sloped portions at the back edges thereof below said pockets; said housing also comprising a backwall whose upper end is entered into said pockets to prevent upward movement of said backwall; said backwall being fiat when removed from said pockets; first means bending said backwall to abut said sloped portions; said circuit breaker also comprising a casing including means defining an area in which said are chute is disposed; a terminal strap to which one of said contacts is mounted; said strap mounted to said housing with said one of said contacts disposed within said area; said first means defining an offset portion of said strap.

5. A circuit breaker comprising a pair of cooperating contacts and an arc chute operatively positioned and constructed to receive and extinguish electric current arcs drawn between said cooperating contacts upon separation thereof; said are chute comprising a plurality of spaced plates and a housing wherein said plates are disposed; said housing comprising spaced sidewalls to which said plates are fixedly secured along the side edges thereof; said sidewalls having rearwardly extending portions defining pockets open at the bottoms thereof; said sidewalls having interfering sloped portions at the back edges thereof below said pockets; said housing also comprising a backwall whose upper end is entered into said pockets to prevent upward movement of said backwall; said backwall being fiat when removed from said pockets; first means bending said backwall to abut said sloped portions; said circuit breaker also comprising a casing including means defining an area in which said are chute is disposed; a terminal strap to which one of said contacts is mounted; said strap mounted to said housing with said one of said contacts disposed within said area; said first means defining an offset portion of said strap; a U-shaped flash barrier partially closing said housing at the front thereof; said casing having means operatively positioning said flash barrier; said sidewalls having forwardly extending portions disposed between the flash barrier U-arms to prevent said arms from converging.

6. The circuit breaker of claim 5 in which the sidewalls comprise a first insulating material which will remain in fixed position when subjected to moisture and said flash barrier comprises a second insulating material which when subjected to moisture will tend to cause the U-arms to converge.

7. A circuit breaker comprising a pair of cooperating contacts and an arc chute operatively positioned and constructed to receive and extinguish electric current arcs drawn between said cooperating contacts upon separation thereof; said are chute comprising a plurality of spaced plates and a housing wherein said plates are disposed; said housing comprising spaced sidewalls to which said plates are fixedly secured along the side edges thereof; said sidewalls having rearwardly extending portions defining pockets open at the bottoms thereof; said housing also comprising a backwall whose upper end is entered into said pockets to prevent upward movement of said backwall; a generally U-shaped flash barrier partially closing the front of said housing; said sidewalls having forwardly extending portions disposed between the flash barrier U-arms to prevent said arms from converging.

8. The circuit breaker of claim 7 in which the sidewalls comprise a first insulating material which will remain in fixed position when subjected to moisture and said flash barrier comprises a second insulating material which when subjected to moisture will tend to cause the U-arms to converge.

9. A circuit breaker comprising a pair of cooperating contacts and an arc chute operatively positioned and constructed to receive and extinguish electric current arcs drawn between said cooperating contacts upon separation thereof; said are chute comprising a plurality of spaced plates and a housing wherein said plates are disposed; said housing comprising spaced sidewalls to which said plates are fixedly secured along the side edges thereof; said sidewalls having rearwardly extending portions defining pockets open at the bottoms thereof; said sidewalls having interfering sloped portions at the back edges thereof below said pockets; said housing also comprising a backwall whose upper end is entered into said pockets to prevent upward movement of said backwall; said backwall being flat when removed from said pockets; first means bending said backwall to abut said sloped portions; a generally U-shaped flash barrier partially closing the front of said housing; said sidewalls having forwardly extending portions disposed between the flash barrier U- arms to prevent said arms from converging.

10. The circuit breaker of claim 9 in which the sidewalls comprise a first insulating material which will remain in fixed poition when subjected to moisture and said flash barrier comprises a second insulating material which when subjected to moisture will tend to cause the U-arms to converge.

References Cited by the Examiner UNITED STATES PATENTS 6/35 Sachs 200-l44 9/55 Gelzheiser et a1. 200-144 

1. A CIRCUIT BREAKER COMPRISING A PAIR OF COOPERATING CONTACTS AND AN ARC CHUTE OPERATIVELY POSITIONED AND CONSTRUCTED TO RECEIVE AND EXTINGUISH ELECTRIC CURRENT ARCS DRAWN BETWEEN SAID COOPERATING CONTACTS UPON SEPARATION THEREOF; SAID ARC CHUTE COMPRISING A PLURALITY OF SPACED PLATES AND A HOUSING WHEREIN SAID PLATES ARE DISPOSED; SAID HOUSING WHEREIN SAID PLATES ARE DISPOSED; PLATES ARE FIXEDLY SECURED ALONG THE SIDE EDGES THEREOF; SAID SIDEWALLS HAVING REARWARDLY EXTENDING PORTIONS DEFINING POCKETS OPEN AT THE BOTTOMS THEREOF; SAID HOUSING 